probe: ProbePointsHelper adjustable minimum points

Factor out minimum required points check for ProbePointsHelper
in prep for setting different values for quad_gantry_level
and z_tilt_adjust

Signed-off-by: John "Fess" Fessenden <fess@fess.org>

klippy/extras/screws_tilt_adjust.py

@@ -46,6 +46,7 @@ class ScrewsTiltAdjust:
         self.probe_helper = probe.ProbePointsHelper(self.config,
                                                     self.probe_finalize,
                                                     default_points=points)
+        self.probe_helper.minimum_points(3)
         # Register command
         self.gcode = self.printer.lookup_object('gcode')
         self.gcode.register_command("SCREWS_TILT_CALCULATE",